Electro-mechanical means of generating subsonic energy



n v s 2,840,176 ELECTRO-MECHANICAL MEANS OF GENERATING SUBSONIC ENERGY Filed Aug. 2, 1955 June 24, 1958 INVENTOR.

ALFRED DAVIS m x%1% FIG.|

MOTOR Y United States aten ELECTRO-MECHANICAL MEANS OF ERATING SUBSONIC ENERGY Alfred Davis, Little Silver, N. 1., assignor to the United States of America as represented by the Secretary of the Army Application August 2, 1955, Serial No. 526,088 2 Claims. (Cl. 181-.5) (Granted under Title 35, 'U. s. Code 1952 s... 266) GEN-' i The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment of any royalty thereon.

The invention relates to a novel apparatus for the A Patented June 24,

the. shaft. 7 A mechano-acoustical device having 'a corn:

pre'ssional surface .or diaphragm pointing in a direction parallel to the axis of the shaft is connected to thesliding member. Thus, as the shaft is driven to rotate, thecom pressional face, is driven backward and forward along a path parallel to the axisof the shaft; The,compressional face is given a sinusoidal oscillation infits medium,

thereby producing compressional'waves'.

' j Referring to Fig.1, ashaft 10 fixedly bears'a drum 12 andisfreely mounted to a housing frame 14 by a bushing 16.. The shaft. 10 isffurth'er supported by being freely I mounted to a support arm 18 of thehousing frame 14 by generation of compressional waves atsubsonic frequeneccentric drive produced a satisfactory movement of the I compressional wave producing mass but wasaccompanied by several undesirable defects. The large unbalanced weight of the eccentric drive gave rise to severe vibrations which tended to injure the housing and-mount for the apparatus. The vibrations also caused undesired mechanical noise within the audio range. The presence of such defects obviously renders the prior art Wave generators unsatisfactory for many uses.

It is a principal object of the present invention to provide a compressional wave generator ject to mechanical vibrations.

It is a further object of the present invention to provide a compressional wave generator capable of operation at subsonic frequencies without the production of mechanical noise. Q

It is a still further object of the invention to provide a subsonic compressionalwave generator'of simple construction and with a minimum number of moving parts.

Further objects and many attendant advantages of the invention .will be readily apparent as the. same becomes better understood from the following detailed description and the accompanying drawings wherein:

Fig. 1 is a side view partially in section of a preferred embodiment of the invention,

Fig. 2 is a front view of the embodiment of Fig. 1,

Fig. 3 is a detail view of a cylindrical cam structure and ring cam follower which are used in the embodiment of Fig. l,

Fig. 4 is a cross section of Fig. 3.

One form of apparatus constructed in accordance with the principles of the invention is an improved generator of compressional waves employing a freely rotating shaft mounted on a housing frame and driven by a motor or other suitable driving means. A tracking .pathis atwhich is not sub a bushing 20. A motor.22 is connected to'oneend of the-shaft .10. They drum .12" has spiral grooving forming a plurality of endless track paths 24 27 seen more clearly in Figs.'3 and'4. g V

Fig.2 shows a front view of'the deviceof Fig.1, with the arm 18'supporting the bushing 20which guidesthe shaft 10. The drum 12 is visible behind the support arm 18. A diaphragm or piston surface 30, is coupled to the forwardedge of the housing frame 14 bya resilient annular gasketor mounting ring 32.

, Fig.3 shows in perspective the paths 2427. This grooving provides the track paths for keys or lugs 34-37 projecting from a cylindrical sliding member 38 which rides freely, axially and circumferentially, along'the surface of. the drum 12. The sliding member 38 is rigidlycoupled' to the center part of the diaphragm 30 which is properly oriented to provide an acoustically eflicient compressional surface in a direction parallel to the axis of the shaft 10. r 7

Fig. 4 is a cross section of the portion 'of the device shown in Fig. 3, taken through the sliding member. The diaphragm 30 is seen coupled to the sliding member 38 whose inwardly projectin keys 34-37 engage correspond- I ing grooves 24-27 in the drum 12 which is secured to the,

, shaft 10. The sliding-member rides freely on the drum.

The grooves 24-27 in the drum 12 *areidfentical and 'are positioned in quadrature relationship to one another about the cylindrical surfaceof the drum; It is obvious,

ofcourse, that any number of grooves and correspond- Q as long as the sliding member ing keys may be provided will be driven satisfactorily.

Upon the rotation of shaft.10 and drum 12 by the operation of motor 22, the force applied to the keys 34-37 causes the sliding member 38 and the diaphragm 30 to oscillate forward and backward along theline of 7 axis of shaft 10. The; oscillation of the diaphragm 30 in .its surrounding medium presents a compressionsurface and accordingly produces compressional waves. Assuming a constant speed of motor, shaft, and drum rotation,

' the'grooves 24-27 are cut to produce a sinusoidal rate of progression of the keys parallel to the shaft which produces a corresponding sinusoidal compressional wave output N Sinusoidal output of compressional waves may also be obtained by a linear rate of spiral ascension of tracking paths along the. drum and a sinusoidal variation of rotatached or inscribed on a cylindrical surface of the shaft or a drum concentric to the shaft to form a cylindrical This tracking path represents a motion produce a sinusoidal motion in the sliding member parallel to the axis of the shaft for. a constant angular velocity of tional speed of the shaft and drum. A sinusoidal va'riation in the speed of rotationcould be achieved, for example, by the use of an alternating current, direct-current series motor in place of the constant speed motor .22.

.=If a supply voltage made up of a sinusoidal alternating current superposed on a direct current supply source is supplied, the rotational speed of motor, shaft and drum will vary at a corresponding sinusoidal rate. Proper values established for the direct current and the alternating current supply will effect the synchronization of the: alternating current frequency and the frequency of oscillation of compressional surface in its medium.

A sinusoidal compressional wave outputis generally preferable, but any other type of compressional wave may I,

be produced'bychanging the 'curve of spiral ascension of the tracking paths along the drum or changing the func-' tion of the rotation variation of the shaft and drum, 0 by a combination oftboth. It is to be understood, of course, thaftheus'e of g'roo such as in tracking pathsft o provide' th'eirr'ieans for driv} ing the sliding member to movetheidi'aph'ragrnis not exclusive method. 7 Tracking may bea'ccornplish'ed by similarly sp'iralling'rails or threads or by any, otheftiack: ing means known to the art with suitable attachments 9') drive the diaphragm. g, 1 f f While there has been described what is at present con sidered to be the preferred embodiment of this invention,

it will be obvious to those skilled in the 'artthat various changes and modifications may be made therein 'With'OIii departing from the invention Having thus described my invention, what is claimed is: 1. A compressional wave generator comprising a vibratable diaphragm having an aperture located therein, a

rigid ring member fastened within said aperture, a rotatable shaft having a cylindrical drum thereon extending loosely Within said ring, a plurality of identical, circum- "feren'tially spaced, i. endless carnming grooves upon 'the surface of said drum, each groove having a cyclic progression along the axis of said shaft with respect to its circumference, and a plurality of circumferentiallyspaced cam-follower lugs extending inwardly from said ring and engaging said grooves, whereby upon rotation of saidshaft said diaphragm is vibrated in accordance with the axial progression of said grooves to produce compressional waves.

2. Awave generator as set forth in claim '1, wherein said grooves are sinusoidally shaped to produce sinusoidal vibration of-said diaphragm upon constant'speed rotation of said shaft.

Aufiero Sept. 19, 1916 Grubman Dec. '19, 1916 'Schroder June 21, 1938 

